A research team from the Department of Applied Physics and Chemical Engineering at Tokyo University of Agriculture and Technology (TUAT), Japan, has achieved a significant breakthrough in nanoscience by overcoming a longstanding challenge in quantum dot (QD) optoelectronics. Their recent study, made available online on March 03, 2026, and published in Volume 14, Issue 11 of the Advanced Optical Materials journal on March 20, 2026, demonstrates that assembling "giant atoms" of colloidal QDs into highly ordered, epitaxially connected superlattices known as QDSLs can revolutionize the performance of next-generation photodetectors.
Colloidal QDs are well-known for their size-tunable band gaps and strong light absorption, making them promising candidates for advanced optoelectronic devices. However, their practical application in photodetectors has been hindered by the low carrier mobility in conventional QD solids, which results from spatial and energetic disorder within the material.
While the team's earlier work, published in 2023 in Nature Communications, significantly enhanced electron mobility by orders of magnitude through the creation of highly ordered quasi-2D QDSLs, a persistent question remained: Would the delocalized charge transport facilitated by these quasi-2D QDSLs diminish the strong quantum confinement effects that bestow QDs with their superior optical properties?
Dr. Satria Zulkarnaen Bisri, an Associate Professor who led the research team, explains, "This new study directly addresses the actual impact of these structural innovations at the mesoscopic level on practical device performance and provides the first evidence that essential quantum confinement effects are effectively preserved, even as charge transport becomes more delocalized in that superlattice."
The findings demonstrate that the epitaxially connected QDSL photodetectors achieve an impressive responsivity of up to 105 A/W and a detectivity of more than 1013 Jones, among the highest values reported for colloidal QD-based photodetectors, operating in the visible and near-infrared ranges. Notably, this performance was achieved in a planar device architecture using only a single monolayer of the superlattice (with a thickness of less than 8 nm), underscoring a direct correlation between enhanced carrier mobility and device sensitivity.
PhD student Dadan Suhendar, who carried out the project, further highlights the other impact of the highly ordered assembly of the QD, "Our analysis of the faster photodetector time response and light-power-dependent trends provides direct evidence of minimum charge trap density within the epitaxially connected lead sulfide (PbS) QDSLs. This result suggests that the well-ordered and highly oriented nature of the superlattice results in significantly fewer surface defects and reduced interface disorder."
According to Dr. Bisri, this achievement is a pivotal step toward the next generation of sensitive, scalable, and ultra-thin light sensors. "By solving the conflict between conductivity and quantum confinement, we have opened the door to new optoelectronic applications from advanced imaging to high-speed communications as well as emerging quantum technologies that align with the future of miniaturized, ubiquitous high-performance technology," Dr. Bisri concludes.
